Question

What is the total surface area of a triangular prism whose height is 30 m and the sides of whose base are 21 m, 20 m and 13 m, respectively?

• A. 1872 sq. m
• B. 1725 sq. m
• C. 1652 sq. m
• D. 1542 sq. m

Answer 1

The correct option is A 1872 sq. m

Total surface area of prism = lateral surface area $+2\times$ (area of base)
Here, $s=\frac{a+b+c}{2}=\frac{21+20+13}{2}=27\therefore Requiredarea=(21+20+13)\times 30+2\times \sqrt{27(27-21)(27-20)(27-13)}=54\times 30+2\sqrt{27\times 6\times 7\times 14}=1620+2\times 126=1872sq.m$